Task ambient luminaires are generally understood to be lighting fixtures which provide light to both a defined target surface and to non-target specific area. Commonly, these type of luminaires are employed in an office context where light is required on a desk surface for task-specific applications and in a direction generally upward for casting light toward the ceiling and walls of the office space. Typically a task ambient luminaire used in the context includes a housing mounted on a wall or office partition above a work surface such as a desk. The housing includes one or more elongated linear lamp tubes and the required electrical components to mount and illuminate the lamp. The housing is further configured, by use of reflectors, etc., to direct light emitted from the lamp downward to the desk surface and upward to an ambient area comprising the ceiling and/or walls. Such task ambient constructions bring the light source closer to the task area and reduce or eliminate direct glare by hiding the lamp tube from view and by controlling the light with suitable lenses, refractors, reflectors, baffles, louvers and the like.
Refractor plates of specialized design are available which will reduce or eliminate both direct glare and reflected glare from a light source. Reflected glare is also known as veiling reflection and results from reflections from a task and the background of the task. For example, light-colored desk surfaces, writing paper thereon and light colored backgrounds reflect desirable light, but if the task (e.g., pencil or ink writing) also reflects light to the viewer, the contrast between the task and its immediate background is reduced. It is this reduction of contrast which makes seeing difficult.
Direct glare can be eliminated by baffles, shields, refractors and reflectors which cut off direct view of the lighting source. As for the elimination of veiling reflections, when their source is light emitted downward from a zone located above and slightly in front of the task area, refractor plates have been employed which refract or redirect the light. This refraction can be visualized in terms of the photometric curves showing relative candlepower distribution of the luminous flux. These curves take the form of a half bat wing shape, or a full bat wing shape if all of the luminous flux below and adjacent to the plane of the refractor is analyzed. The bat wing configurations represent luminous flux patterns and indicate the direction and distribution of the flux.
Typical of refractor plates which distribute luminous flux from a light source in a bat wing configuration are the plates described in U.S. Pat. Nos. 3,258,590 and 4,054,793. However, such reflectors are often fixed in place and offer the user little if no adjustability. Moreover, the mounting of the refractor plates in within the respective luminaires requires installation of fixation means within the luminaire such as mounting tabs on a housing portion of the luminaire and screw holes formed through luminaire reflectors. This type of fixation means complicates production and assembly of the luminaire and can degrade its performance by marring reflector surfaces etc. Addition, typical refractor plates are mounted in such a way as to interfere with the performance of the luminaire's reflectors. That is, refractor plates are often mounted beneath the respective lamp tube at some point upon the downlight luminaire reflector. In this situation, the mounting of the refractor plate impedes passage of light from the lamp tube through the luminaire housing to the task area below.
Thus, there is a need for a device which addresses the issue of veiling reflections caused by a task ambient luminaire, which is readily installed therein in such manner as to minimally interfere with desired light emanations of the luminaire lamp tube, and which is convenient to use and readily adjustable.